The Web Container

The Web container provides a runtime environment for primarily supporting Web-based applications that use the JavaServer Pages (JSP) and/or Servlet J2EE components . A Web container typically exists in the context of a J2EE server that provides both the Web and EJB containers, such as the BEA WebLogic Server 7.0. However, J2EE Web servers do exist that only provide the Web container to support Web applications that serve dynamic content through the employment of Servlets and/or JSPs, for example BEA WebLogic Express 7.0. Because Web applications can also make requests to Web containers for HTML files that contain static content, such as GIF image files, PDF files, and video clips, the Web container is also responsible for serving static content when required.

Note

J2EE Web servers should not be confused with HTTP Web servers, which only handle HTTP/HTTPS requests on behalf of a Web application.

The Web container's runtime environment has the following features:

• Authentication security: The Web container provides login security using customized HTML forms, HTTP server-based security, and mutual authentication using X 5.09 certificates (public key certificates, or PKCs).

• JSP engine: This part of the container translates JSP files into Java servlet code and then compiles and loads the resultant classes into memory. Once in memory, the JSPs execute as servlets.

• Static context server: The Web container serves static content, such as HTML pages, GIF image files, and so on.

• Lifecycle management: Servlet classes are loaded into memory, instances are created, and, if necessary, instances are removed by the Web container. The Web container also maintains various levels of state information for servlets and JSP pages.

• Dispatching: The Web container receives HTTP requests and dispatches them to the proper components, such as JSPs, and Servlets.

• Resource management: The Web container has a timeout mechanism to free the memory resources of inactive servlets. It can also serialize servlet classes to disk in an effort to conserve memory.